Urban sprawl continues to increase. More and more land is being developed on the edges of wilderness or agricultural areas, affecting quality-of-life issues.

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Sprawl, Elena Irwin freely admits, is a “buzzword” — a vague description of a troubling phenomenon. “It gets people’s attention, but it really doesn’t mean much,” she noted. “You can define it in a lot of different ways.”

While Irwin is open to different definitions, the associate professor of environmental economics at Ohio State University has no doubt that Americans are living further from city centers, and further from one another, than ever before. Her previous studies suggest as much; so does common sense. So she was shocked by a 2006 study that found residential development was “no more scattered” in the early 1990s than it was in the mid-1970s.

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The researchers making that counterintuitive claim seemed to have hard evidence on their side, in the form of satellite photos. The team, led by Henry Overman of the London School of Economics, studied 1992 satellite photos of various urban areas in the U.S. and compared them with high-altitude photos taken in 1976. The team’s conclusion: While they continue to grow, our metropolitan areas are just as dense as they were in the 1970s. Specifically, according to the researchers’ report in the Quarterly Journal of Economics, “the proportion of open space surrounding the average residential development” was essentially unchanged over the nearly two decades in question.

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Irwin and a colleague, Nancy Bockstael of the University of Maryland, were both skeptical. So they embarked on their own study, based in part on the remarkably detailed land-use records kept by Howard County, Maryland, an affluent area located between Baltimore and Washington, D.C. They compared that data — which is so complete it includes all of the county’s sidewalks — to the photos taken from space.

“We found the satellite-imagery data does a shockingly poor job at recording low-density development,” Irwin said. Photographing land dominated by two-acre to eight-acre lots, the images revealed only 26 percent of the structures that were recorded in the land-use data. In short: The rooftops of homes nestled among trees on a several-acre lot were easy to miss.

In their research, Irwin and Bockstael compared sets of data from 1973 and 2000 — a somewhat larger spread than the satellite-image study. “Certainly there was a fair amount of development in the 1990s (after the 1992 satellite photos were taken),” she said. But either way — whether the satellite photos missed the homes, or they were built later in the decades — there is a lot more building happening on the edges of wilderness areas than the Overman study suggested. And developing land adjacent to either forests or agricultural fields is a prime indicator of sprawl.

“Think of the land as a patchwork quilt,” Irwin said. She and Irwin studied patches devoted to specific uses, looking specifically at places where developed land (housing or commercial/industrial) bumped up against undeveloped (farmland or forest). No matter how they crunched the numbers, they found “substantial increases” in the number and length of such boundaries, suggesting that development continues to encroach upon the countryside.

What’s more, they found the traditional pattern of infill — that is, suburban areas becoming more densely developed even as the exurbs creep toward the wilderness — does not seem to be occurring. Rather, they found a growing rate of “fragmentation” — that is, development bumping up against undeveloped land — both in the suburbs and the exurbs, suggesting the population is becoming more and more scattered.

Why is this happening?

Irwin suspects telecommuting plays a major role. “With the Internet and other forms of electronic form of communication, some people can substitute part of their need for face-to-face communication with remote communication,” she noted. “Someone might drive into work three days a week and stay at home two days. That lowers the cost of moving further out.”

In addition, many jobs are moving from urban centers to beltways on the periphery. “That means that an employee can move 10 miles further out and still have the same commute,” she said.

While the aesthetic pleasures of living closer to nature are obvious, the phenomenon is causing headaches for regional planners and other policymakers. Even with telecommuting, people living further away from one another tend to drive more, exacerbating a variety of environmental problems. In terms of taxes, cities and counties get hit on both ends. As some of their higher-income residents move out to the periphery, big cities have to deal with a dwindling tax base. Meanwhile, smaller suburbs and county governments must cope with the need for more and better roads and schools. Without question, it costs more money to provide public service to citizens who live far apart.

Irwin and Bockstael do not make any policy recommendations in their paper. To do so, Irwin said, she would need to know more about the motivations of the people who are moving ever outward, away from the city center. A previous study she did in Ohio found that the desire for high-quality schools drove many parents from the city to the suburbs or exurbs. If those findings are confirmed, she said, cities might want to concentrate on improving their educational system in order to retain, or attract back, their higher-income residents.

But such efforts may be in vain: The homesteading desire is deep in the American psyche. Irwin is currently on sabbatical in Switzerland, where the contrast with American cultural attitudes toward the land is striking. “In Europe, you have a lot of preserved open spaces, including publicly accessible forests,” she said. “But there is also much higher-density development. People are more used to living closer together. It’s a much smaller country. They can’t spread out like we can.”